Brushless motor assembly for a fastening tool

ABSTRACT

An electric brushless DC motor is provided including an outer rotor assembly having a metallic rotor body, rotor magnets mounted within an inner surface of the rotor body, and a molded structure formed within the rotor body. The molded structure includes a main body formed on inner surface of the rotor body to securely cover and retain the rotor magnets on the inner surface of the rotor body, an axial fan formed at an end of the rotor body opposite the rotor magnets, and a sense magnet mount formed at approximately a radial center portion of the axial fan. Alternatively or additionally, the molded structure includes a radial member projecting inwardly from the main body towards a center of the outer rotor assembly, and a bearing support member having a substantially cylindrical shape in an axial direction of the outer rotor and supported by the at least one radial member.

RELATED APPLICATION

This disclosure claims the benefit of U.S. Provisional Application No.62/093,803 filed Dec. 18, 2014 and U.S. Provisional Application No.62/093,785 filed Dec. 18, 2014, which are incorporated herein byreference in their entirety.

FIELD OF THE DISCLOSURE

This disclosure relates to power tools. More particularly, the presentinvention relates to brushless motor assembly for a fastening powertool.

BACKGROUND

Finish Nailers are fastening tools used in construction for crownmolding, cabinet molding, door installation, exterior trim and varietyof other finish operations. Finish nailers are may be gas powered,pneumatic or electro-magnetic depending on the source of energy foroperation of nail firing mechanism. An electro-magnetically powerednailer uses a motor as a prime mover that drives a flywheel. Inbattery-powered applications, the motor may be, for example, a brushedDC motor or a brushless DC motor. The nailer battery may include, forexample, Li-Ion/Ni—Cd battery cells. Flywheel runs at a pre-definedspeed, thus storing energy in the form of kinetic energy. This kineticenergy is then transferred to the mechanical linkage that drives thenails.

Finish nailer need a lot less energy as compared to other nailingapplications such as framing, fencing or concrete. The nail sizes aretypically 15Ga to 18Ga in diameter. The main user critical-to-qualityrequirement for a finish nailer is small size and light weight. What istherefore needed is to provide a motor design that is compact yetcapable of outputting sufficient power to drive the fastener.

SUMMARY

According to an embodiment of the invention, an electric brushless DC(BLDC) motor is provided, comprising: an outer rotor assembly having asubstantially-cylindrical metallic rotor body, rotor magnets mountedwithin an inner surface of the rotor body, and a molded structure formedwithin the rotor body. In an embodiment, the molded structure includes amain body formed on an inner surface of the rotor body to securely coverand retain the rotor magnets on the inner surface of the rotor body, anaxial fan formed at an end of the rotor body opposite the rotor magnets,and a sense magnet mount formed at approximately a radial center portionof the axial fan. In an embodiment, the motor further includes a statorassembly received inside the outer rotor assembly and mounted on ashaft; and a sense magnet ring mounted on the sense magnet mount.

In an embodiment, the molded structure includes at least one of a proxy,plastic, or resin material.

In an embodiment, the outer rotor assembly further includes a flywheelintegrally formed on an outer surface of the rotor body.

In an embodiment, the molded structure integrally includes at least oneradial member projecting inwardly from the main body towards a center ofthe outer rotor assembly between the axial fan and the rotor magnets;and a bearing support member having a substantially cylindrical shape inan axial direction of the outer rotor and supported by the at least oneradial member.

In an embodiment, the radial member includes radial fan blades angularlydisposed to generate an airflow with the rotation of the outer rotor.

In an embodiment, the bearing support member is configured to securelyreceive two bearings affixed to the shaft therein.

In an embodiment, the rotor body integrally includes a radial memberprojecting inwardly from the inner surface of the rotor body towards acenter of the outer rotor assembly between the axial fan and the rotormagnets; and a bearing support member having a substantially cylindricalshape in an axial direction of the outer rotor and supported by the atleast one radial member.

In an embodiment, the molded structure also includes a radial portioncovering the ends of the radial member.

In an embodiment, the radial member includes through-holes around thebearing support member to provide airflow communication between theaxial fan and the stator assembly.

In an embodiment, the bearing support member is configured to securelyreceive two bearings affixed to the shaft therein.

According to an embodiment, a power tool is provided including a housingand an electric brushless DC (BLDC) motor according to the abovedescription disposed within the housing.

According to another embodiment of the invention, an electric brushlessDC (BLDC) motor is provided including an outer rotor assembly having asubstantially-cylindrical metallic rotor body, rotor magnets mountedwithin an inner surface of the rotor body, and a molded structure formedwithin the rotor body. In an embodiment, the molded structure integrallyincludes a main body formed on an inner surface of the rotor body, atleast one radial member projecting inwardly from the main body towards acenter of the outer rotor assembly between the axial fan and the rotormagnets, and a bearing support member having a substantially cylindricalshape in an axial direction of the outer rotor and supported by the atleast one radial member. In an embodiment, the motor further includes astator assembly received inside the outer rotor assembly and mounted ona shaft, the shaft being received inside the bearing support member andaffixed rotatably therein via two bearings affixed to the shaft therein.

In an embodiment, the molded structure comprises at least one of aproxy, plastic, or resin material.

In an embodiment, the outer rotor assembly further includes a flywheelintegrally formed on an outer surface of the rotor body.

In an embodiment, the molded structure integrally includes a magnetretention portion covering and retaining the rotor magnets on the innersurface of the rotor body.

In an embodiment, the molded structure integrally includes an axial fanformed at an end of the rotor body opposite the rotor magnets.

In an embodiment, the molded structure integrally includes a sensemagnet mount formed at an end of the bearing support member opposite thestator assembly, the electric motor further comprising a sense magnetring mounted on the sense magnet mount.

In an embodiment, the at least one radial member includes a radial fanblades angularly disposed to generate an airflow with the rotation ofthe outer rotor.

According to an embodiment, a power tool is provided including a housingand an electric brushless DC (BLDC) motor as described above disposedwithin the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of this disclosure in any way.

FIG. 1 depicts a side view of a fastening tool with a housing halfremoved, according to an embodiment;

FIGS. 2A and 2B depict front and back perspective views of an overmoldedouter-rotor brushless motor with an integrated flywheel, according to anembodiment;

FIGS. 3A and 3B depict front and back exploded views of the outer-rotorbrushless motor, according to an embodiment;

FIG. 4 depicts a partially cut-off exploded view of the outer-rotorbrushless motor, according to an embodiment;

FIG. 5 depicts a partially cut-off perspective view of the outer-rotorassembly of the brushless motor, according to an embodiment;

FIG. 6 depicts a perspective view of the outer-rotor main body andflywheel, according to an embodiment;

FIG. 7 depicts a perspective view of the outer-rotor main body withrotor magnets assembled therein, according to an embodiment;

FIGS. 8A and 8B depict front and back views of the outer-rotor main bodywith the fan/rotor molded structure molded therein, according to anembodiment;

FIGS. 9A and 9B depict front and back views of the fan/rotor moldedstructure alone without the rotor main body, according to an embodiment;

FIGS. 10A and 10B depict perspective views of the outer-rotor assemblywith a sense magnet ring prior to and after assembly onto the fan/rotormolded structure, according to an embodiment;

FIG. 11 depicts a perspective view of the outer-rotor having analternative sense magnet ring assembled into the fan/rotor moldedstructure, according to an embodiment;

FIG. 12 depicts a partially cut-off perspective view of an outer-rotorassembly of the brushless motor, according to an alternative embodiment;

FIG. 13 depicts a perspective view of the alternative outer-rotor mainbody and flywheel, according to an embodiment;

FIG. 14 depict a perspective view of the alternative outer-rotor mainbody with the fan/rotor molded structure molded therein, according to anembodiment; and

FIGS. 15A and 15B depict front and back perspective views of a motor endcap, according to an embodiment.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

FIG. 1 depicts a perspective view of a fastening tool 10 (e.g., anailer) with a housing half removed, according to an embodiment. Thefastening tool 10 shown herein includes an outer-rotor brushless DCmotor 100. The outer rotor of the motor 100 is integrally formed with aflywheel 102. In an embodiment, the fastening tool 10 further includes ahousing 12, an input unit 20 housed within a handle 14 of the housingand coupled to an actuator 22 disposed outside the housing 12, and acontrol unit 70. In an embodiment, control unit 70 includes amicro-controller or other programmable control module and powerswitching components for controlling a commutation of the motor 100.Control unit 70 is coupled to a power source (not shown), which may be aDC power source (e.g., a removable battery pack) or an AC power source(e.g., a 120V AC). Control unit 70 is also coupled to the input unit 20via wires 74 and regulates a supply of power from the power source tothe motor 100 based on a logic signal from the input unit 20. Controlunit 70 is coupled to motor terminals via three lead wires 72.

In an embodiment, fastening tool 10 further includes a nosepieceassembly 30 including a contract trip mechanism 32 coupled to thehousing 12, a magazine assembly 40, a driver assembly 50 including adriver 52 and a return mechanism 52, an activation assembly 60, and asolenoid 62, among other components. In an embodiment, actuation of theactuator 22 while contact trip mechanism 32 is in contact with aworkpiece causes the solenoid 62 to engage the activation assembly 62.Activation assembly 62 translates forward and engages the driver 52 toinitiate driving engagement between the driver 52 and the flywheel 102.In an embodiment, the flywheel 102 includes one or more flywheel ringsthat form one or more grooves around the outer surface of the flywheel102. The driver 52 includes corresponding railings that engage thegrooves of the flywheel. Rotation of the flywheel 102 causes the driver52 to accelerate axially and drive a fastener into a workpiece.

The present disclosure is focused on the structure and features of themotor 100. Details of the components and operation of an exemplaryfastening tool are beyond the scope of this disclosure and can be foundin U.S. Pat. No. 6,971,567 and US. Patent Publication No. 2012/0097729,both of which are incorporated herein by reference in their entirety. Itis further noted that while the motor 100 of this disclosure isdescribed with reference to a fastening tool according to an exemplaryembodiment, motor 100 may similarly be used in other power tools andother rotary devices.

FIGS. 2A and 2B depict front and back perspective views of anouter-rotor brushless DC (BLDC) motor 100 with flywheel 102, accordingto an embodiment. In an embodiment, flywheel 102 includes three flywheelannular rings 110 that form grooves 112 there between around the outersurface of the flywheel 102. In an embodiment, flywheel 102 is formedintegrally with rotor 120 on an external circumferential surface of therotor 120 having an increased diameter compared to the remainder of therotor 120. Alternatively, flywheel 102 may be provided as a separatepart attached to an outer surface of the rotor 120. Flywheel 102 may bemade of metal such as steel.

FIGS. 3A and 3B depict front and back exploded views of motor 100,according to an embodiment. FIG. 4 depicts a partially cut-off andpartially-exploded view of the brushless motor 100, according to anembodiment. As shown in these figures, in addition to the outer rotor120, motor 100 includes a stator assembly 130 coupled to a shaft 110,and a motor end cap 140.

In an embodiment, stator assembly 130 includes a stator lamination stack132 having a plurality of stator teeth with slots formed therebetween.Stator windings 134 are wound around the stator teeth defining thephases of the motor 100. In an embodiment, where motor 100 is athree-phase BLDC motor, three windings 134 defining the three phases ofthe motor 100 are disposed around the stator lamination stack 132, eachwinding 134 being wound on opposite two teeth across one another. In anembodiment, stator assembly 130 further includes two end insulators 136attached to the end surfaces of the stator lamination stack 132. In anembodiment, the stator lamination stack 132 is mounted (e.g., viapress-fitting) on a shaft 110.

In an embodiment, motor end cap 140 is disposed at an end of the motor100 and also mounted (e.g., via press-fitting) on the shaft 110 oppositethe stator assembly 130. Motor end cap 140 includes a back plate 142disposed adjacent a fan 122 of the rotor 120 (discussed below) that actsas a baffle for the fan 122. End cap 140 also includes a circumferentialportion 144 with air conduits 146 to redirect the air flow from the fan122 towards other parts of the tool 10, for example, the control unit 70(see FIG. 1). End cap 140 includes a through-hole 148 sized to securelyreceive the shaft 110.

In an embodiment, end cap 140 further includes a rotational positionsensor board 150 therein. Positional sensor board 150 may include, forexample, three Hall sensors 152 facing the rotor 120 and a connector 154projecting outside the back plate 142 to be accessible from outside themotor 100.

The outer-rotor 120 is described herein, according to an embodiment ofthe invention. Use of a flywheel on an outer-rotor of a brushless motoris known. An example of such an assembly is described in U.S. Pat. No.8,047,415, which is incorporated herein by reference in its entirety.The present embodiment describes an improved outer-rotor for a brushlessmotor, wherein in an embodiment, the rotor components, including therotor fan, bearing pocket, etc. are formed within the rotor using asimple mold in an efficient, compact, and easy to manufacture process,as described in detail below.

FIG. 5 depicts a cut-off perspective view of the outer-rotor assembly120, according to a first embodiment of the invention. As shown in thisfigure, and further with reference to FIG. 4, in an embodiment,outer-rotor assembly 120 includes a substantially-cylindrical metallicrotor body 202 on which the flywheel 102, including annular rings 110,is integrally formed. Rotor body 202 and flywheel 102 may be formed ofany metallic material such as steel. Rotor magnets 210 are secured to aninner surface of the rotor body 202. A fan/rotor molded structure 220 ismolded inside the rotor body 202 to form and/or support various rotorassembly 120 components, as discussed herein. In an embodiment,fan/rotor molded structure 220 is formed from epoxy, resin, plastic, orany other moldable non-conductive material.

In an embodiment, the fan/rotor molded structure 220 includes a mainbody 222 formed primarily inside an inner surface of the rotor body 202.The fan/rotor molded structure 220 further includes a plurality ofradial members 204 projecting inwardly from the main body 222 towards acenter of the rotor 120. At the center of the rotor 120, the fan/rotormolded structure 220 forms a bearing support member 224 that supportsone or more shaft ball bearings 214 a, 214 b. The radial members 204 maybe disposed at angularly (i.e., substantially diagonally) so as to formblades of a radial fan that generates airflow with the rotation of therotor 120. Bearing support member 224 may be cylindrical and elongated,sized to press-fittingly receive the bearings 214 a and 214 b. In anembodiment, the bearing support member 224 is disposed along a centerportion of the rotor 120 near the stator assembly 130. As such bothbearings 214 a and 214 b are secured to the rotor assembly 120 on oneside of the stator assembly 130. This arrangement substantially easesthe assembly process.

In an embodiment, the fan/rotor molded structure 220 is additionallyformed with a plurality of blades 228 axially extending from the distalend 226 of the main body 222 to form the axial fan 122 proximate the endcap 140. In an embodiment, main body 202 of the fan/rotor moldedstructure 220 extends to an axial end 232 of the rotor main body 202opposite the fan 122 to cover the rotor permanent magnets 210 on theinner surface of the rotor main body 202. In an embodiment, bearingsupport member 224 of the fan/rotor molded structure 220 additionallyincludes a sense magnet mount 230 for sense magnet ring 212 in thevicinity of the fan 122. These features are described herein in detail.

It is noted that while the fan/rotor molded structure 220 herein may beobtained using any molding mechanisms such as over-molding,insert-molding or injection-molding.

FIG. 6 depicts a perspective view of the substantially-cylindrical rotorbody 202 including the flywheel 102, without the fan/rotor moldedstructure 220, according to an embodiment. As discussed above, theflywheel 102 includes two or more annular rings 110 on the outer surfaceof the rotor body 202 near one end, forming one or more annular grooves112 therebetween.

FIG. 7 depicts the rotor body 202 including the flywheel 102, with rotormagnets 210 mounted therein, according to an embodiment. In anembodiment, four permanent magnets (e.g., ferrite or rare earth magnets)210 are securely placed inside an inner surface of the rotor body 202.In an embodiment, the inner surface of the rotor body 202 may include amounting portion 240 that is recessed from the rest of its inner surface242 where the flywheel 102 is located, such that the surface of themagnet 210 is substantially on the same cylindrical plane as the surface242. In an embodiment, the magnets 210 will magnetically attach to therotor body 202, though alternatively or additionally an adhesive may beused to secure the magnets 210 to the rotor body 202. In an embodiment,the magnets 210 are mounted on a distal end of the rotor body 202opposite the flywheel 102.

FIGS. 8A and 8B depict front and back perspective views of rotorassembly 120 including the flywheel 110 and rotor body 202, with thefan/rotor molded structure 220 molded therein, according to anembodiment. In this step of the assembly process, in an embodiment, theflywheel 110 and rotor body 202, including the magnets 210, are placedin a mold machine and the fan/rotor molded structure 220 is molded inthe area inside the flywheel 110 and rotor body 202 in one molding step.The molding forms the radial fan blades 204, the axial fan 112, thebearing support member 224, and the sense magnet mount 230, allintegrally as a part of a single molded structure.

FIGS. 9A and 9B depict front and back perspective views of the fan/rotormolded structure 220 without the flywheel 110 and rotor body 202,according to an embodiment. As shown in these figures, extending from amain body 222 of the fan/rotor molded structure 220 is a magnetretention portion 252 with magnet pockets 250 around the rotor magnets210 when the molding process is completed. In this embodiment, the rotormagnets 210 are completely covered with a layer of the molding of themagnet retention portion 252 disposed between the rotor magnets 210 andthe stator assembly 130. It must be understood that alternativeembodiments where the molding only partially covers the magnets 210 iswithin the scope of this disclosure.

In an embodiment, an inner surface of the main body 222 and the magnetcover portion 252 of the fan/rotor molded structure 220 aresubstantially formed along a same cylindrical plane. This cylindricalplane forms an opening 256 through which the stator assembly 130 isreceived within the rotor assembly 120.

In an embodiment, the fan/rotor molded structure 220 additionallyincludes radial fan blades 204 and bearing support member 224, includingsense magnet mount 230 with retention features 274 for mounting andsupporting sense magnet ring 212, as described above. In an embodiment,the fan/rotor molded structure 220 additionally includes blades 228axially extending from the distal end 226 of the main body 222 to formthe axial fan 122 proximate the end cap 140, as described above.

Referring back to FIGS. 8A and 8B, in an embodiment, once the moldingprocess is complete, a spacer (or bushing) 216 is inserted into bearingsupport member 224, and rotor bearings 214 a and 214 b are press-fittedinto the bearing support member 224 at the two ends of the spacer 216.In an embodiment, first bearing 214 a is press-fittingly insertedaxially into the bearing support member 224. The bearing support member224 includes a first lip 260 (see FIG. 5) on its inner surface againstwhich the first bearing 214 a sits when fully inserted. Then, bearingspacer 216 is inserted into the opening of the bearing support member224 opposite the first bearing 214 a. Finally, the second bearing 214 bis press-fittingly inserted into the bearing support member 224 until incomes in contact with a second lip 262 (see FIG. 5). In an alternativeor additional embodiment, the bearings 214 a, 214 b may be securedinside the support structure via an adhesive.

In an embodiment, a distal end 264 of the bearing support member 224where the second bearing 214 b is located may slightly protrude from theend of the second bearing 214 b. This portion of the bearing supportmember 224 may be crimped by, for example, heat-staking to axiallyretain the second bearing 214 b within the bearing support member 224.The first bearing 214 a may be axially retained via the sense magnetring 212, as discussed below.

In an embodiment, as described above, the bearing support member 224 isattached to the main body 222 of the fan/rotor molded structure 220 viathe radial fan blades 204. In an embodiment, the bearing supportstructure is radially aligned with the flywheel 102.

The arrangement of two rotor bearings within the bearing support member224 of the fan/rotor molded structure 220 as described above offersseveral advantages. First, the rotor assembly 120 is supported on themotor shaft 110 by two bearings 214 a, 214 b that are both axiallyarranged on one side of the stator assembly 130. This greatly simplifiesthe assembly process, as the stator 130 can be assembled into theopening 246 of the rotor assembly 120 after the rotor assembly processis complete. Furthermore, the stator windings 134 become easilyaccessible on one side of the stator 130 opposite the bearing supportmember 224. As shown in FIG. 1, the three motor wires 72 from thecontrol unit 70 read the stator 130 from one side of the motor 100 andare coupled (via soldering, fusing, etc.) directly to the statorwindings 134. This greatly simplifies the routing and connectivity ofthe motor wires 72. Additionally, both bearings 214 a, 214 b aresupported via a single structure, which saves space and material.Finally, the bearing support member 224 is supported by the radial fanblades 204, which further saves on space and material.

FIGS. 10A and 10B depict perspective views of rotor assembly 120, priorto and after the assembly of sense magnet ring 212, respectively,according to an embodiment. In an embodiment, the sense magnet ring 212is a single piece magnet forms in the shape of a ring. The ring includesfour magnetic poles that are aligned with the four poles of the rotor120, i.e., with the four rotor magnets 210. The ring is positioned atclose proximity to rotational position sensor board 150 (e.g. Hallsensor board) to allow the sensors 152 to detect the rotational positionof the sense magnet ring 212, and thereby the rotor 120.

According to an embodiment of the invention, the sense magnet ring 212includes projecting transition areas 270 aligned with the rotor magnets210, and recessed areas 272 disposed between the projecting transitionareas 270. In an embodiment, the transition areas between adjacent polesof the sense magnet ring are located at approximately the centers of theprojecting transition areas 270. In other words, the ends of theopposite poles meet near the center of the projecting transition areas270. The recessed areas 272 may be recessed radially or axially (or bothaxially and radially) with respect to the radially-projecting transitionareas 270. In other words, the projecting transition areas 270 may beradially projecting with respect to an outer periphery of the recessedareas 272, or axially projecting with respect to an outer plate of therecessed areas 272. With this arrangement, the transition areas 270 havea higher magnetic flux as sensed by the sensors 152, allowing thesensors 152 to detect the magnetic transition between the poles moreefficiently.

In an embodiment, and end of the bearing support structure 224 of thefan/rotor molded structure 220 includes sense magnet mount 230 havingalignment and retention features 274 that receive and support the sensemagnet ring 212. The alignment and retention features 274 include fouraxial projection formed around the periphery of the axial end of thebearing support structure224. In an embodiment, the radially-projectingtransition areas 270 of the sense magnet ring 212 are received betweenthe axial projections 274 of sense magnet mount 230. In an embodiment,sense magnet mount 230 may also include a notch or a similar keyingfeature for proper polar alignment of the sense magnet ring 212 with thesense magnet mount 230. In this manner, the mount and support for thesense magnet ring 212 is provided in the molding of the fan/rotor moldedstructure 224.

FIG. 11 depicts an alternative sense magnet ring 212 having transitionareas 280 that are raised axially, but not radially, with respect to aplane of the recessed areas 282. This arrangement may be preferred wherethe positional sensors 152 (e.g., Hall sensors) are disposed furtherfrom the sense magnet 212 in the axial direction. In an embodiment, thering 212 includes through-holes within the recessed areas 282 and thesense magnet mount 230 at the end of the bearing support structure 224of the fan/rotor molded structure 220 includes corresponding legs 284arranged to mate with the through-holes of the sense magnet ring 212.

A rotor assembly 320 is described herein with reference to FIGS. 12-14,according to an alternative embodiment of the invention.

FIG. 12 depicts a cut-off perspective view of the outer-rotor assembly300, according to an embodiment of the invention. As shown in thisfigure, in an embodiment, outer-rotor assembly 300 includes asubstantially-cylindrical metallic rotor body 302 on which the flywheel102, including annular rings 110, is integrally formed. Rotor body 302and flywheel 102 may be formed of any metallic material such as steel.Rotor magnets 210 are secured to an inner surface of the rotor body 302.A fan/rotor molded structure 320 is molded inside the rotor body 202 toform and/or support various rotor assembly 300 components, as discussedherein. In an embodiment, fan/rotor molded structure 320 is formed fromepoxy, resin, plastic, or any other moldable non-conductive material.

FIG. 13 depicts a perspective view of the rotor assembly 300 with rotorbody 302, but without the fan/rotor molded structure 320, according toan embodiment. FIG. 14 depicts a perspective view of rotor assembly 120including the fan/rotor molded structure 220 molded onto the rotor body302, according to an embodiment. In this embodiment, with reference tothese figures and FIG. 12, the rotor body 302 integrally includes, inaddition to the flywheel 102, a radial support plate 304 extendingradially inwardly from the main body 302 towards a center of the rotorassembly 300, and a bearing support member 324 formed at the end of theradial support plate 304. In an embodiment, bearing support member 324is substantially cylindrical-shaped and elongated, sized topress-fittingly receive and support one or more shaft ball bearings 214a, 214 b, and a spacer 216 therebetween. In an embodiment, radialsupport plate 304 includes a plurality of axial through-holes 306 thataround the bearing support member 324. Accordingly, in this embodiment,unlike the embodiment of FIGS. 5-11, the bearing support is formed as apart of the metallic rotor body 302.

In an embodiment, the fan/rotor molded structure 320 is similar to theprevious embodiment, but is formed around the two sides of the radialsupport plate 304 and the bearing support member 324. In thisembodiment, fan/rotor molded structure 320 includes a first mold portion322 that forms blades 328 of axial fan 322 at the end of the main body302, and a sense magnet ring support portion 360 at the end of thebearing support member 324 for mounting the sense magnet ring 312. Thefan/rotor molded structure 320 also includes a second mold portion 324that is formed around the rotor magnets 210. In an embodiment, the firstand second mold portions 322, 324 are connected together through thethrough-holes 306.

FIGS. 15A and 15B depict front and back perspective views of a motor endcap 140, according to an embodiment. In this embodiment, the motor endcap 140 includes a through-hole 148 that receives the motor shaft and aback plate 142 (i.e., a baffle) that is arranged in parallel to theaxial fan 122 of the motor 100. At the periphery of the back plate 142is provided a cylindrical circumferential portion 144 that mates withthe end of the flywheel 102. The circumferential portion 144 receivesthe axial fan 122, as well as a portion of the bearing support structure224 and the sense magnet ring 212 therein. The circumferential portion144 includes two air conduits 146 that allow hot air generated by thefans through the motor to be expelled.

In an embodiment, end cap 140 further includes a rotational positionsensor board 150 therein. Positional sensor board 150 may include, forexample, three Hall sensors 152 facing the rotor 120 and a connector 154projecting outside the back plate 142 to be accessible from outside themotor 100.

In an embodiment, the back plate 142 includes a slot 155. Positionalsensor board 150 (e.g., Hall sensor PCB) is mounted on the inside of theback plate 142. In an embodiment, the board 150 includes a curvedportion shaped to be disposed around the through-hole 148. Thepositional sensor board 150 includes three positional sensors 152disposed around the through-hole 148. When the motor is fully assembled,the positional sensors 152 are in close proximity to theaxially-projecting (or radially-raised) transition areas 270 of thesense-magnet ring 212 for an accurate rotational reading of the rotor120. In an embodiment, a back surface of the positional sensor boardincludes connector 154 (including, e.g., three terminals for the threesensors) that is exposed through the slot 155. This arrangement allowsthe connection port to be accessible from outside the motor withouthaving to route wires directly to the Hall sensors.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

1. An electric brushless DC (BLDC) motor comprising: an outer rotor assembly having a substantially-cylindrical metallic rotor body, a plurality of rotor magnets mounted within an inner surface of the rotor body, and a molded structure formed within the rotor body, the molded structure comprising a main body formed on an inner surface of the rotor body to securely cover and retain the rotor magnets on the inner surface of the rotor body, an axial fan formed at an end of the rotor body opposite the rotor magnets, and a sense magnet mount formed at approximately a radial center portion of the axial fan; a stator assembly received inside the outer rotor assembly and mounted on a shaft; and a sense magnet ring mounted on the sense magnet mount.
 2. The electric motor of claim 1, wherein the molded structure comprises at least one of a proxy, plastic, or resin material.
 3. The electric motor of claim 1, the outer rotor assembly further comprising a flywheel integrally formed on an outer surface of the rotor body.
 4. The electric motor of claim 1, wherein the molded structure integrally comprises: at least one radial member projecting inwardly from the main body towards a center of the outer rotor assembly between the axial fan and the rotor magnets; and a bearing support member having a substantially cylindrical shape in an axial direction of the outer rotor and supported by the at least one radial member.
 5. The electric motor of claim 4, wherein the at least one radial member comprises a plurality of radial fan blades angularly disposed to generate an airflow with the rotation of the outer rotor.
 6. The electric motor of claim 4, wherein the bearing support member is configured to securely receive two bearings affixed to the shaft therein.
 7. The electric motor of claim 1, wherein the rotor body integrally comprises: a radial member projecting inwardly from the inner surface of the rotor body towards a center of the outer rotor assembly between the axial fan and the rotor magnets; and a bearing support member having a substantially cylindrical shape in an axial direction of the outer rotor and supported by the at least one radial member.
 8. The electric motor of claim 7, wherein the molded structure also includes a radial portion covering the ends of the radial member.
 9. The electric motor of claim 7, wherein the radial member includes through-holes around the bearing support member to provide airflow communication between the axial fan and the stator assembly.
 10. The electric motor of claim 7, wherein the bearing support member is configured to securely receive two bearings affixed to the shaft therein.
 11. The electric motor of claim 1, further comprising an end cap affixed to an end of the outer rotor assembly opposite the stator assembly, the end cap including a positional sensor board disposed in close axial proximity to the sense magnet ring.
 12. The electric motor of claim 1, wherein the stator assembly comprises a plurality of stator teeth and a plurality of stator windings formed around the stator teeth, the stator windings being accessible for connection of a plurality of lead wires from an open end of the outer rotor assembly opposite the sense magnet mount.
 13. A power tool comprising a housing and an electric brushless DC (BLDC) motor according to claim 1 disposed within the housing.
 14. An electric brushless DC (BLDC) motor comprising: an outer rotor assembly having a substantially-cylindrical metallic rotor body, a plurality of rotor magnets mounted within an inner surface of the rotor body, and a molded structure formed within the rotor body, the molded structure integrally comprising a main body formed on an inner surface of the rotor body, at least one radial member projecting inwardly from the main body towards a center of the outer rotor assembly between the axial fan and the rotor magnets, and a bearing support member having a substantially cylindrical shape in an axial direction of the outer rotor and supported by the at least one radial member; and a stator assembly received inside the outer rotor assembly and mounted on a shaft, the shaft being received inside the bearing support member and affixed rotatably therein via two bearings affixed to the shaft therein.
 15. The electric motor of claim 14, wherein the molded structure comprises at least one of a proxy, plastic, or resin material.
 16. The electric motor of claim 14, the outer rotor assembly further comprising a flywheel integrally formed on an outer surface of the rotor body.
 17. The electric motor of claim 14, wherein the molded structure integrally comprises a magnet retention portion covering and retaining the rotor magnets on the inner surface of the rotor body.
 18. The electric motor of claim 14, wherein the molded structure integrally comprises an axial fan formed at an end of the rotor body opposite the rotor magnets.
 19. The electric motor of claim 14, wherein the molded structure integrally comprises a sense magnet mount formed at an end of the bearing support member opposite the stator assembly, the electric motor further comprising a sense magnet ring mounted on the sense magnet mount.
 20. The electric motor of claim 19, further comprising an end cap affixed to an end of the outer rotor assembly opposite the stator assembly, the end cap including a positional sensor board disposed in close axial proximity to the sense magnet ring.
 21. The electric motor of claim 14, wherein the at least one radial member comprises a plurality of radial fan blades angularly disposed to generate an airflow with the rotation of the outer rotor.
 22. The electric motor of claim 14, wherein the stator assembly comprises a plurality of stator teeth and a plurality of stator windings formed around the stator teeth, the stator windings being accessible for connection of a plurality of lead wires from an open end of the outer rotor assembly opposite the bearing support member.
 23. A power tool comprising a housing and an electric brushless DC (BLDC) motor according to claim 14 disposed within the housing. 